You've got to get your hands on a Hot Dog costume (can be earned in the Styling Lounge when you reach Level 7) or the French Fry costume (get this on the Catwalk after completing the runway task).

Then meet us when we start in the Party Plaza and slowly make our way through the public rooms; the more, the merrier so invite your friends! We want to fill the rooms with our costumes, so take a look at the picture below for an idea :)